When performing an infusion into a patient, or in other similar cases, an indwelling needle connected to an infusion line is made to puncture a blood vessel of the patient and to indwell within the blood vessel. The intended operation is conducted under this condition.
Such an indwelling needle includes a hollow outer needle, an outer needle hub firmly attached to a proximal end of the outer needle, an inner needle having a sharp needle point at its distal end and which is inserted through the outer needle, and an inner needle hub firmly attached to a proximal end of the inner needle (see, for example, International Publication No. WO 2006/027923 A1.
When the indwelling needle is made to puncture the patient's blood vessel, the puncturing operation is conducted in an assembled condition where the inner needle is inserted into the outer needle, and the needle point of the inner needle protrudes from the distal end of the outer needle. In the assembled condition, normally, the outer needle hub is connected with the connector of an infusion line.
Thereafter, when the needle point of the inner needle reaches the inside of the blood vessel, blood flowing in through the opening at the needle point passes through the lumen of the inner needle, and flows into the inside of a transparent inner needle hub (flashback). This enables confirmation (visual confirmation) that the inner needle has punctured the blood vessel securely.
After flashback is confirmed, the outer needle is advanced so that the outer needle becomes inserted into the blood vessel.
Next, while gripping the outer needle by hand, the inner needle is pulled out of the outer needle. Then, an infusion agent is dispensed through the infusion line and the outer needle, which are connected to each other.
Meanwhile, a seal member (plug body) is provided on (affixed to) the outer needle hub. The seal member has a slit through which the inner needle can be inserted and which is closed when the inserted inner needle is pulled out. In other words, the seal member has a self-closing property.
It has been a common practice that, when the indwelling needle having the seal member as mentioned above is set in an assembled condition by inserting the inner needle into and through the seal member, the inner needle is inserted into the seal member, starting with its easier-to-insert side, namely, starting with the needle point thereof. In this instance, there has been a fear that friction between the seal member and the needle point may be generated, resulting in damage to the needle point (chipping of the cutting edge). In addition, the insertion of the inner needle starting with the needle point thereof may cause the slit (seal member) to be unintentionally ruptured by the needle point. Unintentional rupture of the slit, if it occurs, may cause the slit, for example, to become deviated from its original shape. In this case, when the inner needle is pulled out from the seal member while using the indwelling needle assembly in an assembled condition, comparatively heavy friction may be generated between the seal member and the needle body, thus making it difficult to perform the pulling-out operation.